Such pipettes are known as comprise a piston movable in a cylinder, a longitudinal pinion rack on the piston shaft, and a pawl engaging the pinion rack due to the force of a spring. The pawl is connected to an operating member with which the pawl is forced to move the upwards pulled pinion rack and thus also the piston downwards in steps with a desired length. The length of the step can also be adjusted by a cover plate movable on or on the side of the pinion rack or by a pawl lifter, which determines the position where the downwards moving pawl engages the pinion rack. Such pipettes are presented for instance in the publications DE-A-2926691, FI-A-844096 and FI-A-931650.
On the market there has also been a stepping pipette (Socorex Stepper 411) having a ratchet wheel and a co-operating pawl journaled on a separate shaft, and a gearwheel rotating with the ratchet wheel and moving the piston of the pipette.